This invention relates to an inkjet printhead. More particularly, the invention relates to a Moving Nozzle Ink Jet With Inlet Restriction.
Most ink jet printheads of the type manufactured using micro-electro mechanical systems (MEMS) technology have been proposed in a construction using nozzle chambers formed in MEMS layers on the top of a substrate with nozzle chambers formed in the layers. Each chamber is provided with a movable paddle actuated by some form of actuator to force ink in a drop through the nozzle associated with the chamber upon receipt of an electrical signal to the actuator. Such a construction is typified by the disclosure in my International Patent Application PCT/AU99/00894.
The present invention stems from the realisation that there are advantages to be gained by dispensing with the paddles and causing ink drops to be forced from the nozzle by decreasing the size of the nozzle chamber. It has been realised that this can be achieved by causing the actuator to move the nozzle itself downwardly in the chamber thus dispensing with the paddle, simplifying construction and providing an environment which is less prone to the leakage of ink from the nozzle chamber.
According to the invention there is provided an ink jet printhead including:
a plurality of nozzles each adapted to eject drops of ink toward a surface to be printed; wherein,
each of the nozzles has an external actuator, an apertured roof portion and an ink baffle formation; the roof portion defining an inner surface for contacting the ink and an outer surface opposite the inner surface, the outer surface being operatively connected to the external actuator such that the actuator moves the roof portion away from the surface to be printed to eject the ink using back pressure at least partially provided by the baffle formation.
Preferably, the nozzles each have an associated nozzle chamber adapted to be supplied with ink via at least one conduit in an underlying substrate, the nozzle chamber being defined by a floor portion having a peripheral sidewall and the roof portion having a depending peripheral sidewall, the sidewalls of the floor and roof portions being arranged to overlap in a telescopic manner, wherein the baffle formation is an opening in the floor portion, through which the conduit in the underlying substrate communicates with the nozzle chamber, said opening being sufficiently small in area to provide back pressure in use to the ink within the chamber when the roof portion is moved downwardly toward the floor portion.
Preferably, the substrate adjacent said opening is used to accommodate ancillary components.
Preferably, the ancillary components include power traces.
Preferably, the ancillary components include signal traces.